Field of the Invention
The present invention generally relates to devices for moving objects, and more specifically to a method and device for transferring mobility-impaired persons, such as moving a hospital patient from a bed to a table.
Description of the Related Art
A wide variety of products have been designed to move objects from one location to another and, in particular, transfer mobility-impaired individuals such as patients. In a hospital or other medical setting, patients must often be transported from their beds to an examination table or operating table, and back again. Basic devices for transferring patients include stretchers that are carried manually by two attendants, and gurneys that can more easily be handled by a single attendant. A typical gurney (British trolley) has an elongate patient-support surface, a frame or chassis structure for the patient-support surface, and wheels or casters that facilitate movement of the gurney.
One innovation in the field of patient-transfer devices is the use of two counter-rotating belts for the patient-support surface which creep under the patient to provide “frictionless” acquisition and delivery. An example of such a design is shown in U.S. Pat. No. 5,540,321 (Foster). The attendant manually rotates a crank to move the upper and lower belt trays under the patient while the belts counter-rotate. Once the patient is supported by the trays, the tray assembly is raised off the bed and the device can be rolled on casters to transport the patient.
The entire Foster device moves during use, either closer to the patient/bed during acquisition, or away from the patient/bed during delivery. The mechanism that drives this lateral movement is the forcible engagement of the lower belt against the bed. Because movement of the lower belt drives the lateral movement of the device, the relative belt speed (eversion rate for both belts) is the same as the lateral speed of the support structure. The matching belt speed is relative to the table assembly, so technically one side of a given belt (upper or lower) will be moving at twice the table speed from a fixed point of reference, and the other side of the given belt will have zero speed from the fixed point of reference.
This inherent matching of the belt speed and lateral device speed carries through to a variety of patient moving devices. For example, U.S. Pat. No. 6,932,209 (Kasagami et al.) illustrates a patient transfer device which is motorized rather than relying on manual actuation. Kasagami is not technically a gurney since it does not have a frame or chassis on wheels, and it is used to transfer a patient from a bed to a gurney, but it still operates on the principle of two counter-rotating belts to avoid slippage between the patient and the upper belt. As with Foster, the lateral movement of the Kasagami device is driven by the lower belt itself, and so the lateral movement speed again matches the rotational speed of both belts.
Another patient transfer device which utilizes the two counter-rotating belts is illustrated in U.S. Pat. No. 7,540,044 (Patterson et al.). One representation of the Patterson invention is shown in FIG. 1. Patient transfer device 10 is generally comprised of a table assembly 12, a slide assembly 14, a support structure or frame 16, a device base 18, wheels or casters 20, and a control keyboard 22. Table assembly 12 is mounted on horizontal slide assembly 14 affixed to frame 16 to provide lateral movement to/from the patient's bed during acquisition/delivery. Patterson also teaches synchronizing the belt and table speeds such that there is no shearing between the patient and the surface of the upper belt, or between the bed and the surface of the lower belt.
While the use of two counter-rotating belts to crawl under a patient greatly reduces frictional engagement which ideally eliminates skin shear for the patient, the prior art patient transfer devices can still create significant patient discomfort. The Foster device can be particularly jerky since it is manually driven without any speed control. The motor-driven Kasagami device improves in this regard, but does not always move evenly to/from the patient since it has no tracks or rails to guide the lateral movement, so multiple attendants may be required to help position the device in order to easily acquire the patient. The Patterson device further improves in this regard by using the slide assembly to keep the table assembly properly aligned and smoothly move under the patient, but even with the Patterson device some patients still have described an uncomfortable pushing sensation on the body.
In light of the foregoing, it would be desirable to devise an improved patient transfer device and transfer method which provided a more comfortable patient acquisition experience. It would be further advantageous if the device and method could adapt to patients having different characteristics such as weight.